Once downloaded you must active the trial within 10 days, although this version of the OS does not require a product key to be evaluated. The trial version is a "full working version of Windows 7 Enterprise" but if you decide to continue using it with a proper licence after your 90 days of trial are over you will need to do a clean install of it. At the end of your testing period, the OS will shut down once every hour.

Windows 7 Enterprise licenses are only available to businesses which are customers of Microsoft's Software Assurance volume licensing program and are not available through retail or to OEM, so if you are impressed by your trial and want to deploy Windows 7 in your business you will have to sign up to the scheme or look as the similar versions of Windows 7 which have wider availability. Find out more about this trial in the FAQ.